Probiotic problems: Mastitis marketing flawed, say researchers

A paper claiming the marketing of probiotics to treat mastitis is problematic has caused a controversy, but probiotics researchers and manufacturers say the science is sound.

A paper in the International Breastfeeding Journal ​has raised concerns about the marketing of probiotic products to treat mastitis.

Lisa Amir, associate professor at La Trobe University in Australia, and colleagues say this marketing is based on a single piece of flawed research.

The disputed paper in question - Arroyo et al's Treatment of infectious mastitis during lactation: antibiotics versus oral administration of Lactobacilli isolated from breast milk​ published in Clinical Infectious Diseases​ – has been used by several probiotic product manufacturers in Australian advertising as the sole reference to support the effectiveness of probiotics to help prevent or treat mastitis.

Mastitis is often caused by a build-up of milk within the breast because of feeding problems and in some cases this built-up milk can become infected with bacteria like Staphylococcus.​

A 2000 review of data by the World Health Organisation​ ​(WHO) found the incidence of mastitis and breast abscess occur in all populations regardless of breastfeeding norms, with reported rates varying from few to 33% of lactating women.

Trial discrepancies​

But Amir raises a number of issues with the paper, which compared the effectiveness of probiotics and antibiotics for treating mastitis, including a discrepancy between the published results and the clinical trials registry, which refer to different data collection points.

Secondly, while the trial was described as blinded randomised and controlled, Amir notes that subjects assigned to the antibiotics group were given prescriptions by their own doctors – meaning the subjects and clinicians were not blinded.

She also suggests the choice of antibiotics may not have been appropriate, and questions why only the symptom of breast pain was recorded.

Amir’s paper, which also challenges why Australian advertising authorities have allowed manufacturers to market probiotics to medical professionals on such slim evidence, has caused a stir in Australia, with a number of legal and medical journals calling for tighter regulation of probiotic marketing.

Mónica Olivares, head of research and development at Biosearch Life, told us the firm has been in touch with Amir and the co-authors to clarify “misunderstandings​” and draw their attention to additional research.

“The Arroyo study is just the first of a different number of studies performed with L. fermentum CECT5716. We are aware of the methodology limitations of the study, but what it was key about it, is that evidenced the capability of L. fermentum CECT5716 to reduce the bacterial load in breast milk. The study encouraged us to continue with the clinical development of the strain​,” said Olivares.

She cited a 2015 paper by Maldonado-Lobon et al., – “Lactobacillus fermentum CECT 5716 Reduces Staphylococcus Load in the Breastmilk of Lactating Mothers Suffering Breast Pain: A Randomized Controlled Trial​” – published in Breastfeeding Medicine​ as the other main published evidence.

She also said an additional paper in this area was currently under preparation.

NutraIngredients also contacted Juan Rodríguez, professor at Complutense University of Madrid and corresponding author for the Arroyo study.

He took responsibility for the discrepancies between the paper and the trial registry, saying he neglected to update the registry with the final methodology after the research had been completed.

Rodríguez also defended how antibiotics were used in the trial, noting the ethics committee disallowed the use of a placebo.

Instead, subjects’ doctors were asked to prescribe whatever treatment they would normally, to mimic “real-life​” practice.

He also emphasised the research’s independence.

“Please, note that we are a research group working in a public university in Madrid, Spain, and, therefore, we had no pressure at all from any company (and still we work in the same way). The transfer of the strain to a company happened a few years later and we were not involved in the deal​.”

Amir confirmed a number of probiotic companies had been in touch with her following the publication of her paper. But she said she has not yet been able to read or respond to this information.

“I did read everything published to date carefully and even if there are ‘omissions’, more evidence is needed before these products can be promoted as having evidence. Some studies have shown reduced bacterial counts in milk, but this is not the same as clinical mastitis – which is what counts for women and clinicians​,” Amir told us.

She said she has applied for a grant to conduct a large trial of the prevention of mastitis with probiotics.